two GPS relative precision

Hello,

I want to equip two autonomous boats with GPS to track their position.

From what I’ve read, the precision of the GPS position is in the order of some metres.

What I’m wondering is that, if the boats were at a distance of 10m, what would be the measured distance using the two GPS positions?

I don’t care much about the absolute positioning error, as long as both boats are affected by the same error, so that their relative positioning is somewhat precise.

Anyone has any info on that? Obviously the boats would operate in an harbour so not in a cluttered environment.

A post with a similar question viewtopic.php?t=17191

And a partial answer could be found here http://wiki.orbswarm.com/index.php?titl … Tek_EB-85a

Angelo